Capillaries are the exchange vessels. They are microscopic and have only one wall—tunica intima—allowing substances to pass through quickly.

How do systemic and pulmonary circulations differ?

Systemic circulation is the pathway of blood from the left ventricle of the heart through the aorta and other arteries to all parts of the body. Pulmonary circulation is the pathway of blood from the right ventricle to the pulmonary artery to lung arterioles and capillaries. After the exchange of gases, blood is returned to the left atrium of the heart.

What is the hepatic portal circulation?

Route of blood flow through the liver

How is fetal circulation different from adult circulation?

The circulation in a fetus includes three structures that close at birth. The first structure is the ductus venosus (allows most of the blood to bypass the immature liver of the developing baby and empty directly into the inferior vena cava). The other two structures allow most of the blood to bypass the developing lungs: the foramen ovale (shunts blood from the right atrium to the left atrium) and ductus arteriosus (connects aorta and the pulmonary artery).

How does the blood pressure gradient explain blood flow?

When a blood pressure gradient is present, the blood circulates; conversely, when a blood pressure gradient is not present, blood does not circulate.

Name four factors that influence blood pressure.

Blood volume, strength of each heart contraction, heart rate, and the thickness of the blood